The present invention relates to an apparatus and method for mounting and dismantling an elongate wear body adapted to slidably contact a clothing that travels in a loop in a paper making machine.
Paper making processes often employ suction devices that slidably contact one surface of a wire, fabric, or other clothing the opposite surface of which may support a paper web for transporting the web through various devices in a paper making machine. Various types of suction devices are used, for example, for suctioning water from the paper web and clothing to dewater the web, or for suctioning water and fibers from a clothing after the web has been transferred from the clothing so as to clean the clothing. Suction devices typically include wear ledges that extend along the clothing in the cross-machine direction and have wear surfaces adapted to slidably contact the clothing. A known type of suction box has its wear ledges detachably mounted to support bodies by means of a plurality of bolts distributed along the suction box. The bolts are accessible from the long side of the suction box and, to detach the wear ledges, the wire or felt must be removed from the paper machine so that the bolts become accessible to be loosened and the wear ledges become exposed for removal and replacement with new wear ledges. This procedure is time-consuming and results in a considerable production fall-off.
To overcome these problems associated with the mounting and dismantling of the wear ledges, a suction box has been proposed in which each wear ledge is connected to the support body by means of longitudinal, cooperating elements in the shape of a T-groove in the wear ledge and a corresponding T-shaped protrusion in the support body so that the wear ledge can be removed from the support body by being moved in its longitudinal direction, i.e., in the cross-machine direction, whereupon a new wear ledge is slid onto the T-shaped protrusion to mount the wear ledge onto the support body. Relatively large clearance is necessary between the walls of the T-groove and the T-shaped protrusion to enable such a movement of the wear ledge. Consequently, vibrations can develop in the wear ledge during machine operation and the desired width of the suction gap in the suction box cannot be maintained.
U.S. Pat. No. 5,078,835 describes ledges for resilient support of a wire. Each ledge has a stationary support part and a part that is movable in relation thereto, which movable part is provided with a wear ledge on its outer, free end. The movable part is moved to its operating position by means of a pressure cushion that is pressurized and thereby caused to expand. When the pressure in the pressure cushion ceases, the wear ledge resumes its resting position by means of a spring. The movable part has a support body to which the wear ledge is detachably mounted by means of T-shaped grooves and protrusions. As the wear ledge is not rigidly mounted to the support body during operation, disturbing vibrations can develop in the wear ledge and be transmitted to the wire. Furthermore, if fluid pressure to the pressure cushion should fail during operation, the wear ledge will not be held in its desired operating position.
U.S. Pat. No. 5,129,992 describes a support with a wear ledge for a wire, and a locking device provided with a spring member or an inflatable body. The locking device, by means of a tensioned spring or an inflated body, clamps the wear ledge in its active position, the tilt angle of which is adjusted by way of wedge members. The wear ledge has a dovetail guide with either a large interspace or an additional low-friction layer to enable dismantling of the wear ledge. During operation, the wear ledge is not rigidly fixed in the dovetail guide.
U.S. Pat. No. 5,486,270 describes a foil with a locking device and a support for a wear ledge. The locking device comprises an inflatable body or a number of springs for fixing the wear ledge in an active position elevated from the support by inflating the body or tensioning the springs. The angle between the wear ledge and the wire can be adjusted by means of displaceable wedges arranged on the downstream side of the locking device. The wear ledge is mounted with a dovetail guide without being rigidly fixed during operation.
DE-A1-42 42 658 describes dewatering ledges that have rigid supports and pressure hoses arranged thereon, which pressure hoses, when inflated, retain the wear ledges in an operating position via a movable support body, on which the wear ledge is detachably mounted by means of T-shaped grooves and protrusions. As the wear ledge is not rigidly mounted on the support body during operation, disturbing vibrations can develop in the wear ledge and be transmitted to the wire. Additionally, if fluid pressure to the hoses should fail during operation, the wear ledges will not be retained in the desired operating positions.
U.S. Pat. No. 4,559,105 describes a foil that has a rigid support body and a wear ledge that is detachably mounted to the support body by means of T-shaped grooves and protrusions, which furthermore allow movement of the wear ledge in relation to the support body with the aid of an inflatable element that is arranged in the T-groove so as to act directly on the wear ledge and retain the same in its operative position. A risk of vibrations in the wear ledge is inherent in this construction and becomes especially serious when the inflatable element breaks or when, for any reason, its pressurization diminishes or ceases entirely.
The above needs are addressed by the present invention, which provides an apparatus for mounting a wear body in which the wear body is continuously urged by spring elements into a stable operating position in engagement with a support body, the spring elements causing a locking member to engage clamping surfaces of the wear body and lock it in the stable operating position, thereby eliminating or substantially reducing vibrations of the wear body during operation. For dismantling the wear body from its support body, an actuator is provided. The actuator is operable to move the locking member against the force of the spring elements so as to disengage the locking member from the clam ping surface s of the wear body. Preferably, the locking member comprises an elongate locking bar disposed in an elongate mounting track defined in the wear body. Accordingly, once the actuator is actuated and the locking bar is moved into a release position disengaged from the clamping surfaces, the wear body can be slid in the cross-machine direction so as to disengage it from the locking bar.
Thus, in accordance with a preferred embodiment of the invention, an apparatus for slidably contacting a clothing that carries a paper web and travels in a loop along a machine direction in a paper making machine includes an elongate support body extending in a cross-machine direction, the support body defining at least one cavity therein and at least one opening that extends into the cavity and is open facing the clothing. The apparatus further includes an elongate wear body supported on the support body and extending in the cross-machine direction, the wear body and support body defining opposing cooperative support surfaces, a wear surface of the wear body being adapted to slidably contact the clothing, the wear body defining a mounting track therein extending in the cross-machine direction, the mounting track defining clamping surfaces therein. A locking member is engaged in the mounting track of the wear body, the locking member being configured to be movable toward and away from the support body between a clamped position in engagement with the clamping surfaces of the mounting track and a release position disengaged from the clamping surfaces, the locking member in the release position being freely slidable within the mounting track in the cross-machine direction. At least one locking device is disposed in the cavity of the support body and has a connecting element extending through the opening and connected to the locking member, the connecting element being movable toward and away from the wear body, the locking device including a spring member connected between the support body and the connecting element and operable to apply a continuous force to the connecting element so as to bias the locking member into the clamped position in engagement with the clamping surfaces and thereby urge the wear body against the support surface of the support body to lock the wear body in a stable operating position. The locking device further includes an actuator disposed in the cavity of the support body and operable upon actuation thereof to move the connecting element against the force of the spring member so as to move the locking member into the release position to permit the wear body to be slidably dismantled from the apparatus.
Preferably, the cavity in the support body is elongated in the cross-machine direction, and a plurality of openings are defined in the support body extending from the cavity and open toward the clothing, the openings being spaced along the support body in the cross-machine direction. The locking device preferably includes an elongate press bar disposed in the cavity and a plurality of connecting elements connected to the press bar and extending through the openings in the support body and connected to the locking member. The locking device preferably also includes a spring member connected between each connecting element and the press bar for continuously biasing the connecting elements to urge the locking member into the clamped position.
In a preferred embodiment of the invention, the support surface of the support body faces toward the clothing and the support surface of the wear body faces away from the clothing, and the locking device is operable to retract the locking member away from the clothing to lock the wear body in a stable operating position and to extend the locking member toward the clothing to permit the wear body to be removed from the apparatus. The spring members advantageously comprise compression spring members disposed between a first surface of the press bar that faces the wear body and a surface of the support body that faces away from the wear body. The actuator is advantageously disposed between a second surface of the press bar that faces away from the wear body and a surface of the support body that faces toward the wear body. The actuator preferably comprises a fluid-actuated device such as an inflatable hose or the like, but may alternatively comprise an eccentric shaft that can be rotated to move the connecting elements against the force of the spring elements, a sealed pressure chamber formed in a portion of the cavity in the support body, or a plurality of small hydraulic or pneumatic cylinders disposed in the cavity. The spring members advantageously comprise a plurality of spring washers stacked one atop another, but may also comprise coil springs or the like.
In accordance with a further preferred embodiment of the invention, the wear body and the support body include cooperating guide elements configured to engage each other and guide the wear body into the stable operating position, the guide elements also fixing the wear body in a predetermined position in the machine direction relative to the support body. The guide element of the wear body preferably comprises a pair of wall sections defining opposing side surfaces spaced apart in the machine direction, the side surfaces defining an outer portion of the mounting track. The guide element of the support body preferably comprises a protrusion formed on the support body and configured to be received at least partially into the outer portion of the mounting track, the protrusion including opposite side surfaces configured to engage the side surfaces of the wall sections.
The invention also provides a method for mounting and removing an elongate wear body adapted to slidably contact a clothing that travels in a loop along a machine direction in a paper making machine, the wear body being of the type defining an elongate mounting track therein extending through at least one end of the wear body and along the wear body in a cross-machine direction and defining a wear surface adapted to slidably contact the clothing, the mounting track defining clamping surfaces therein, the mounting track defining an outer portion that is open at a surface of the wear body on an opposite side thereof from the wear surface. A method in accordance with a preferred embodiment of the invention comprises mounting the wear body by slidably inserting an elongate locking member into the mounting track, and continuously urging the wear body into engagement with an elongate support body configured to support the wear body in a stable operating position, the wear body being urged into the operating position by spring elements connected to the support body and to the locking member, the spring elements urging the locking member against the clamping surfaces so as to lock the wear body in the operating position. Dismantling the wear body is accomplished by actuating an actuator in operative engagement with the locking member so as to move the locking member against the force of the spring elements and disengage the locking member from the clamping surfaces, and sliding the wear body in the cross-machine direction relative to the locking member so as to disengage the wear body from the locking member.
The invention thus facilitates the stable mounting of the wear body during operation so that vibrations of the wear body are eliminated or substantially reduced, and yet the wear body can be easily dismantled by virtue of the locking member being freely slidable in the cross-machine direction within the mounting track when it is disengaged from the clamping surfaces by activation of the actuator. Moreover, the proper location of the wear body in its operating position does not depend on the proper functioning of a fluid-actuated device as in some prior devices.